US2014257770A1PendingUtilityA1
Numerical simulation method for the flight-icing of helicopter rotary-wings
Est. expiryNov 30, 2031(~5.4 yrs left)· nominal 20-yr term from priority
Inventors:Ming Lu
G06F 30/20G06F 30/15G06F 2111/10G06F 30/28G06F 17/5009
38
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Claims
Abstract
The present invention is related to a numerical simulation method for the flight-icing of helicopter rotary-wings. This invention includes the algorithm of adding the voracity compensation force term to the momentum and energy equations describing the air-supercooled water droplets two-phase rotational flows in the single fluid two-phase flow system in wake domain of helicopter-rotary wings; the algorithm of adding the centrifugal and Coriolis force to the slip velocity equation; the models describing the water film and icing progress containing the effect of the centrifugal and Coriolis force; and the procedure using the above algorithms and models to do simulation.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A numerical simulation method for the flight-icing of helicopter rotary-wings comprise an algorithm of adding the VCF (Vorticity Compensation Force) term to the momentum and energy equations describing the air-SWD (Supercooled water Droplets) two-phase rotational flows in the single fluid two-phase flow system in wake domain of helicopter-rotary wings; an algorithm of adding the centrifugal and Coriolis force to the slip velocity equation; models describing the WF (Water Film) movement and icing progress containing the effect of the centrifugal and Coriolis force; an procedure using the above algorithms and models to simulate the flight-icing of helicopter rotary-wings using computer codes running on computers.
2 . The method of claim 1 , wherein said added Vorticity Compensation Force is obtained by the density ρ m of said air-SWD single fluid two-phase flow being multiplied by an unit vorticity diffusion compensation vector {right arrow over (f)} ω , which has the expression as
{right arrow over (f)} ω ={right arrow over (n)} ω ×( v m (∇ 2 {right arrow over (ω)} m ) R c ),
where, {right arrow over (n)} ω being the maximum gradient direction of vorticity magnitude;
v ω being a contravariant numerical viscosity, as a scalar variable, with the same dimension as the fluid kinemics viscosity;
R c being a characteristic radii of the vorticity compensation;
{right arrow over (ω)} m , being a vorticity of said air-SWD single fluid two-phase flow;
symbol×being the cross-product operation;
symbol ∇ 2 being the Laplacian operator.
3 . The method of claim 2 , wherein said contravariant numerical viscosity v ω is defined as
v ω ≡{right arrow over (v)} m •{right arrow over (n)},
where {right arrow over (v)} ω being a numerical viscosity vector; {right arrow over (n)}=└n x , n y , n z ┘ being an unit normal direction vector of computing grid interfaces; symbol•being the dot-product.
4 . The method of claim 3 , wherein said numerical viscosity vector {right arrow over (v)} ω is defined as
v
->
ω
=
R
->
ω
2
ω
->
,
where {right arrow over (R)} ω being a radii vector of the compensated voracity.
5 . The method of claim 1 , wherein said act of adding the centrifugal and Coriolis force to the slip velocity equation includes that said centrifugal and Coriolis force are in form of body force vector.
6 . The method of claim 1 , wherein said models describing the WF movement and icing progress containing the effect of the centrifugal and Coriolis force can derive {right arrow over (V)} f , the velocity vector on the plane (, c) at height η in said WF based on the local coordinator system (η,ξ,ζ), the {right arrow over (V)} f is written as
V
->
f
(
ξ
,
ϛ
,
η
)
=
K
_
_
·
η
[
τ
->
m
μ
m
-
ρ
w
(
h
f
-
η
)
μ
w
f
->
gcf
]
,
where μ w and ρ w is the kinematic viscosity and density of said WF; at the interface between said WF and said air-SWD two-phase flows, {right arrow over (τ)} m is the shear stress vector in direction (ξ,ζ) and μ m is the kinematic viscosity of said mixture; h f is the height of said WF; {right arrow over (f)} gcf is the projected summation of the unit gravity {right arrow over (g)} and centrifugal {right arrow over (f)} centr on the local coordinator system K is the Coriolis coefficient tensor.
7 . The method of claim 6 , wherein said Coriolis coefficient tensor K is expressed as
K
_
_
=
[
1
-
k
3
k
2
k
3
1
-
k
1
-
k
2
k
1
1
]
,
where the element [k 1 , k 2 , k 3 ] are the three components of the vector {right arrow over (k)} in the direction (ξ,ζ,η); and {right arrow over (k)} is expressed as
k
->
=
[
k
1
,
k
2
,
k
3
]
T
=
-
2
ρ
w
η
(
h
f
-
η
)
μ
w
ω
->
OZ
,
f
,
where {right arrow over (ω)} OZ,f is the projection of helicopter rotary-wing rotating speed of {right arrow over (ω)} OZ on said local coordinator system (η,ξ,ζ).
8 . The method of claim 1 , wherein said procedure to simulate the flight-icing of helicopter rotary-wings includes the following steps
(1) build the rotating frame of reference and generate the computing grid around the un-iced rotary-wings; (2) divide the whole computational domain into three sub-domains: the far-filed, near-filed and wake domain; (3) specify the initial time t; (4) solve the governing equations for the air and SWD flows at the far-field domain to obtain the velocity, density, pressure, temperature, turbulence of air flow and the velocity of SDW; (5) solve the governing equations for the air-SWD single fluid two-phase mixture flows at the near-field and wake domain to obtain the pressure p m , velocity {right arrow over (V)} m , temperature T m , dynamic viscosity μ m , and shear stress τ m ; (6) solve the WF movement equation to obtain {right arrow over (V)} f , the velocity of the WF and find the WF thickness h f ; (7) solve the icing progress model to find the ice thickness and obtain the iced configuration of rotary-wings; (8) regenerate the computing grid; (9) go back to step (2) for the computation at the next time (t+Δt).Cited by (0)
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